Structural Complexity and Distance from Source Habitat Determine Invertebrate Abundance and Diversity

The structural complexity of habitats and the distance from the dispersion source are considered important determinants of species diversity. The fractal dimensions of substrates are a strong alternative measure for quantifying the structural complexity. In this paper, we tested the hypothesis that structural complexity and distance from a dispersion source affect the density and diversity of macro‐invertebrates on submersed macrophytes. To test this hypothesis, we used artificial substrates with different fractal dimensions, which were incubated at different distances from a dispersion source (a stand of macrophytes) in a Neotropical floodplain lake. The relationship between the structural complexity of macrophytes and the density and diversity of invertebrates attached to artificial substrates was positive and significant. On the other hand, distance from the dispersion source negatively affected both the density and diversity of the attached invertebrates. For Oligochaeta, however, there was a significant effect of structural complexity for the artificial plants positioned further away, but it was not significant in the plants positioned closer to the dispersion source. Thus, the effects of complexity depended on the distance from the dispersion source, at least for this specific group of macro‐invertebrates. These results suggest that both structural complexity and distance from the dispersion source should be considered together to explain the diversity of invertebrates in river–floodplain systems. In addition, our results show that there is great potential for using fractal dimensions as a tool to quantify structural complexity in aquatic habitats, especially at the small spatial scales perceived by macro‐invertebrates. Abstract in Portuguese is available at http://www.blackwell‐synergy.com/loi/btp .     

Comparing the invasibility of experimental "reefs" with field observations of natural reefs and artificial structures

Natural systems are increasingly being modified by the addition of artificial habitats which may facilitate invasion. Where invaders are able to disperse from artificial habitats, their impact may spread to surrounding natural communities and therefore it is important to investigate potential factors that reduce or enhance invasibility. We surveyed the distribution of non-indigenous and native invertebrates and algae between artificial habitats and natural reefs in a marine subtidal system. We also deployed sandstone plates as experimental 'reefs' and manipulated the orientation, starting assemblage and degree of shading. Invertebrates (non-indigenous and native) appeared to be responding to similar environmental factors (e.g. orientation) and occupied most space on artificial structures and to a lesser extent reef walls. Non-indigenous invertebrates are less successful than native invertebrates on horizontal reefs despite functional similarities. Manipulative experiments revealed that even when non-indigenous invertebrates invade vertical "reefs", they are unlikely to gain a foothold and never exceed covers of native invertebrates (regardless of space availability). Community ecology suggests that invertebrates will dominate reef walls and algae horizontal reefs due to functional differences, however our surveys revealed that native algae dominate both vertical and horizontal reefs in shallow estuarine systems. Few non-indigenous algae were sampled in the study, however where invasive algal species are present in a system, they may present a threat to reef communities. Our findings suggest that non-indigenous species are less successful at occupying space on reef compared to artificial structures, and manipulations of biotic and abiotic conditions (primarily orientation and to a lesser extent biotic resistance) on experimental "reefs" explained a large portion of this variation, however they could not fully explain the magnitude of differences.     

Colonization and production of macroinvertebrates on artificial substrata: upstream–downstream responses to a leaf litter exclusion manipulation

1. Macroinvertebrate colonization dynamics were examined on artificial substrata in a stream with terrestrial litter inputs excluded, downstream of the litter-exclusion treatment, and in a reference stream. 2. Short-term examination of the rates of organic matter accrual and invertebrate colonization demonstrated significantly lower accumulation of leaf detritus and invertebrates in the litter-excluded reach and a short distance downstream of that reach. 3. All major fractions of organic matter and invertebrates declined on artificial substrata during the 3-year litter exclusion. Further, secondary production on artificial substrata in the litter-excluded reach decreased from 6.2 to 1.5 g AFDM m⁻² year⁻¹ from pretreatment to the third year of litter exclusion, respectively. 4. Downstream, fine particulate organic matter on artificial substrata decreased during litter exclusion, and there was a significant reduction in colonization of collector-filterers. Total secondary production downstream of the litter exclusion declined >70%, demonstrating that downstream colonization dynamics are linked to upstream detritus inputs and processing by stream invertebrates.     

The underestimated importance of belowground carbon input for forest soil animal food webs

The present study investigated the relative importance of leaf and root carbon input for soil invertebrates. Experimental plots were established at the Swiss Canopy Crane (SCC) site where the forest canopy was enriched with ¹³C depleted CO₂ at a target CO₂ concentration of c . 540 p.p.m. We exchanged litter between labelled and unlabelled areas resulting in four treatments: (i) leaf litter and roots labelled, (ii) only leaf litter labelled, (iii) only roots labelled and (iv) unlabelled controls. In plots with only ¹³C-labelled roots most of the soil invertebrates studied were significantly depleted in ¹³C, e.g. earthworms, chilopods, gastropods, diplurans, collembolans, mites and isopods, indicating that these taxa predominantly obtain their carbon from belowground input. In plots with only ¹³C-labelled leaf litter only three taxa, including, e.g. juvenile Glomeris spp. (Diplopoda), were significantly depleted in ¹³C suggesting that the majority of soil invertebrates obtain its carbon from roots. This is in stark contrast to the view that decomposer food webs are based on litter input from aboveground.     

Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 μm (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants.     

Aquarium studies on the consumption of small animals by O–group grass carp, Ctenopharyngodon idella (Val.)

In aquarium experiments common invertebrates from streams and ponds were offered to O-group grass carp, Ctenopharyngodon idella (Val.) in the presence of palatable plants. When there was no cover for the prey to hide under, the carp ate many of the invertebrates, but when stones were provided, considerably more invertebrates escaped. Rainbow trout eggs were not eaten, but trout fry were taken as soon as they had emerged from artificial spawning redds. While searching for food, grass carp never disturbed the stones covering possible food organisms.     

Postcanine dental form in the mustelidae and viverridae (Carnivora: Mammalia)

This study investigates whether the gross morphology of mustelid and viverrid postcanine dentitions corresponds with differences in diet. For each species, the predominant foods ingested are used to form predictions of dental form and measurements of the carnassial and molar teeth determine the extent of shearing and crushing surfaces on the postcanine teeth. Principal components analysis distinguishes species according to morphological differences in the dentition and these differences are compared with predictions of dental form based on diet. Dietarily specialized species are more likely to be correspondingly specialized in the dentition and species with varied food sources are more likely to possess dental characteristics that are generalized in function. Consumers of foods with high fracture resistance, such as vertebrate tissue and hard-surfaced invertebrates, possess specialized shearing or crushing postcanine teeth. On the other hand, species that consume foods of lesser fracture resistance, such as fruit and soft invertebrates, differ greatly in dental form and are more generalized in dental function. A few species possess postcanine dentitions that do not correspond with diet; the absence of dental-dietary correlation in these species suggests that other factors, such as phylogeny, are important in determining dental form.     

Responses of benthic invertebrates in an experimental channel to artificial flushes

A large experimental channel was used to examine the responses of benthic invertebrate communities to artificial flushes. Two artificial flushes were done at a 20-day interval with a 2-fold difference in peak discharge and duration between them. The effects of the flushes on macroinvertebrates were monitored by comparing the abundance of individual taxa, taxon richness, diversity measures, and similarity indices. Taxon richness and abundances of invertebrates were drastically reduced by every flush. However, the diversity of invertebrates was not significantly reduced by the flushes, and the composition was similar before and after each flush. The fast recruitment of some taxa, having short life cycles, reduced the diversity of invertebrates in the interval between the two flushes. The flushes caused significant reductions in the abundance of epiphytes and fauna living in the streambed. The fauna more resistant to flushes were invertebrates that fasten their cases or retreats by silk threads to substrata. Taxa living in sediment under stones and having a sucking apparatus were also resistant to flushes. Handling editor: R. Bailey     

Three-dimensional analysis of mandibular dental root morphology in hominoids

Although often preserved in the fossil record, mandibular dental roots are rarely used for evolutionary studies. This study qualitatively and quantitatively characterizes the three-dimensional morphology of hominoid dental roots. The sample comprises extant apes as well as two fossil species, Khoratpithecus piriyai and Ouranopithecus macedoniensis. The morphological differences between extant genera are observed, quantified and tested for their potential in systematics. Dental roots are imaged using X-ray computerized tomography, conventional microtomography and synchrotron microtomography. Resulting data attest to the high association between taxonomy and tooth root morphology, both qualitatively and quantitatively. A cladistic analysis based on the dental root characters resulted in a tree topology congruent with the consensus phylogeny of hominoids, suggesting that tooth roots might provide useful information in reconstructing hominoid phylogeny. Finally, the evolution of the dental root morphology in apes is discussed.     

Rapid Assessment of Lepidoptera Predation Rates in Neotropical Forest Fragments1

The mechanisms underlying responses of invertebrates to forest edges remain poorly understood. Here, we use an experimental approach to investigate the predation rates on butterflies in two neotropical forest fragments. Neither distance from forest edge nor degree of forest openness affected predation rates on artificial caterpillars. The mean predation rate of artificial caterpillars on Barro Colorado Island (1500 ha) was significantly higher than that on Peninsula Gigante (2600 ha) likely due to density‐dependent effects. Our study demonstrates the utility of artificial predation experiments for rapid assessment of relative lepidoptera predation rates in tropical forests.     

Colonization of fine particulate organic matter by invertebrates in a Central Florida stream

Abstract. Our study was conducted to determine whether small invertebrates of the shredder and collector feeding guilds would preferentially colonize fine particulate organic matter (FPOM) from fast-decaying species of leaves in central Florida streams. Bags of FPOM (0.2–1 mm) generated from maple, elm, sweetgum, and water oak leaves, as well as artificial Sty-rofoam, were suspended at two sites in Poley Creek, a 1st-order sand-bottomed stream. Three replicate bags of each type were collected from each site after 7, 14, and 28 d, and bacteria and invertebrates present were counted. Bacteria colonized maple and elm in significantly higher numbers than sweetgum, oak and Styrofoam. The amphipod Gammarus tigrinis accounted for 97% of all shredders in FPOM bags, and 63% of total invertebrates. Deposit-feeding chi-ronomids comprised 87% of collectors and 28% of total invertebrates. No other taxon comprised >2% of total invertebrates. Large numbers of invertebrates colonized in the first 7 d, but densities did not increase after Day 7. Both shredders and total invertebrates occurred in significantly greater densities on maple and elm than on sweetgum and oak. Amounts of FPOM remaining in bags after 28 d were significantly smaller for maple and elm (P<.05), suggesting that shredders were eating the FPOM. Collectors occurred in similar densities in all natural FPOM bags. Only a few individuals of either functional feeding group colonized Styrofoam bags, suggesting that FPOM was being colonized for its nutritional value rather than as a refuge from predation.     

Hydraulic influences on periphyton and benthic macroinvertebrates: simulating the effects of upstream bed roughness

1. Hydraulic conditions, periphyton biomass and invertebrate communities were compared on artificial substrates exposed to a range of upstream roughness conditions across an area of uniform current velocity and depth in a gravel-bedded river. The effect of river bed roughness was simulated by installing roughness elements upstream of artificial substrates.
2. Increasing upstream roughness reduced the average near-bed velocity above the substrates and increased short-term variability in velocity (i.e. turbulence).
3. Periphyton chlorophyll a density showed a general decline with near-bed velocity and was significantly lower on the substrates exposed to the river bed reference and 0 mm roughness treatments than the 110 mm roughness elements. Chlorophyll a was also negatively correlated with the abundance of larger collector-browsing invertebrates. This indicates that effects of the changes in hydraulic conditions on invertebrates may have contributed to the observed treatment effects on periphyton.
4. Invertebrate abundance and diversity declined with increasing upstream roughness. Filter-feeders, collector-browsers and predatory invertebrates all declined in abundance with increasing upstream roughness, but the effect was strongest for filter-feeders. Eight of the nine most common taxa showed significant treatment effects. The orthoclad chironomid, Eukiefferiella sp., was not influenced strongly by upstream roughness, but its abundance was correlated significantly with periphyton biomass.     

Hydraulic influences on periphyton and benthic macroinvertebrates: simulating the effects of upstream bed roughness

1. Hydraulic conditions, periphyton biomass and invertebrate communities were compared on artificial substrates exposed to a range of upstream roughness conditions across an area of uniform current velocity and depth in a gravel-bedded river. The effect of river bed roughness was simulated by installing roughness elements upstream of artificial substrates.
2. Increasing upstream roughness reduced the average near-bed velocity above the substrates and increased short-term variability in velocity (i.e. turbulence).
3. Periphyton chlorophyll a density showed a general decline with near-bed velocity and was significantly lower on the substrates exposed to the river bed reference and 0 mm roughness treatments than the 110 mm roughness elements. Chlorophyll a was also negatively correlated with the abundance of larger collector-browsing invertebrates. This indicates that effects of the changes in hydraulic conditions on invertebrates may have contributed to the observed treatment effects on periphyton.
4. Invertebrate abundance and diversity declined with increasing upstream roughness. Filter-feeders, collector-browsers and predatory invertebrates all declined in abundance with increasing upstream roughness, but the effect was strongest for filter-feeders. Eight of the nine most common taxa showed significant treatment effects. The orthoclad chironomid, Eukiefferiella sp., was not influenced strongly by upstream roughness, but its abundance was correlated significantly with periphyton biomass.     

Uptake and transport of lead by perennial ryegrass from flowing solution culture with a controlled concentration of lead

Summary Perennial ryegrass was grown in flowing solution culture in a glasshouse, and during February lead was added to the nutrient solution and held at a constant concentration; uptake and transport of lead were followed in conditions of low intensity daylight or higher intensity artificial light. Uptake of lead by the roots was most rapid during the first 4 days after addition to the nutrient solution. After this time there was a steady increase in uptake per g dry weight of root with plants grown in artificial light having a much higher rate of uptake than plants grown in daylight. Roots always contained more lead than the corresponding shoots and concentration was always greater in the roots than in the shoots. The concentration in both roots and shoots increased with time but that in plants grown in artificial light was higher than that in plants grown in daylight. Two phases of uptake were identified, an initial rapid phase which is probably an exchange phenomenon, and a slow sustained phase which may be under metabolic control. A lower proportion of the total lead taken up remained in the roots of plants grown in artificial light than in those grown in daylight. This difference may have resulted from differences in (i) the production of organic carriers and/or (ii) transpiration. re]19750930     

Marine antifouling laboratory bioassays: an overview of their diversity

In aquatic environments, biofouling is a natural process of colonization of submerged surfaces, either living or artificial, involving a wide range of organisms from bacteria to invertebrates. Antifouling can be defined as preventing the attachment of organisms onto surfaces. This article reviews the laboratory bioassays that have been developed for studying the control of algae and invertebrates by epibiosis (chemical ecology) and the screening of new active compounds (natural products and biocides) to inhibit settlement or adhesion, ie fouling-release coatings. The assays utilize a range of organisms (mainly marine bacteria, diatoms, algae, barnacles). The main attributes of assays for micro- and macroorganisms are described in terms of their main characteristics and depending on the biological process assessed (growth, adhesion, toxicity, behavior). The validation of bioassays is also discussed.     

Assessment of non-target impact of 1080-poisoning for vertebrate pest control on weta (Orthoptera: Anostostomatidae and Rhaphidophoridae) and other invertebrates in artificial refuges

Artificial refuges and mark-recapture techniques were used to monitor the non-target impacts of handbroadcast application (simulating aerial application) of Wanganui No.7 cereal-based baits containing 0.15% (1500 µg g-1) 1080 on populations of weta and other invertebrates in Tararua Forest Park, North Island, New Zealand. Wellington tree weta (Hemideina crassidens) and a cave weta (Isoplectron sp.) were the only species of weta that occupied the refuges. Flatworms, slugs, spiders, harvestmen, amphipods, millipedes, centipedes, cockroaches, and beetles also occupied the refuges. Invertebrate numbers in the refuges were monitored for 12 months before and 4 months after bait application on 22 August 2000. Bait application had no significant impact on the numbers of either species of weta, or on slugs, spiders, and cockroaches, the most numerous other invertebrates occupying the refuges. Bait application also had no effect on the number of individually marked tree weta resighted in the refuges. Few weta or other invertebrates were observed on baits at night. The concentration of 1080 in a cave weta collected alive from a bait, and in a tree weta collected alive from outside an artificial refuge, was less than 10% of the average lethal dose. The results indicate that 1080-poisoning for vertebrate pest control is unlikely to have any negative impact on populations of weta or the other invertebrates monitored.     

Metamorphosis of <Emphasis Type="Italic">Hydractinia echinata</Emphasis>—natural versus artificial induction and developmental plasticity

Many marine invertebrates reproduce through a larval stage. The settlement and metamorphosis of most of the species are synchronised and induced by environmental organisms, mainly bacteria. The hydrozoan Hydractinia echinata has become a model organism for metamorphosis of marine invertebrates. In this species, bacteria, e.g. Pseudoalteromonas espejiana, are the natural inducers of metamorphosis. Like in other species of marine invertebrates, metamorphosis can be induced artificially by monovalent cations, e.g. Cs⁺. In this study, we present systematic data that metamorphosis—with both inducing compounds, the natural one from bacteria and the artificial one Cs⁺—are indeed similar with respect to (a) the morphological progression, (b) the localisation of the primary induction signal in the larva, (c) the pattern of apoptotic cells occurring during the initial 10 h of metamorphosis and (d) the disappearance of RFamide-dependent immunocytochemical signals in sensory neurons during this process. However, a difference occurs during the development of the anterior end, insofar as apoptotic cells and settlement appear earlier in planulae induced with bacteria. Thus, basically, Cs⁺ may be used as an artificial inducer, mimicking the natural process. However, differences in the appearance of apoptotic cells and in settlement raise the question of how enormous developmental plasticity in hydrozoans actually can be, and how this is related to the absence of malignant devolution in hydrozoans.     

Duftstoffe im Erdreich. Flüchtige Metabolite als Infochemikalien

Volatile metabolites diffuse not only in the atmosphere to possess their actions aboveground, but also belowground living organisms benefit from volatiles in the soil since they can act as communication signals, defence and chemo‐attraction compounds, as well as mediators for cell‐to‐cell recognition. Various eucaryotes (e.g. plant (roots), invertebrates, fungi) and also procaryotes (e.g. rhizobacteria) are verifiable involved in these volatile mediated interactions.     

Preparation of artificial seeds using cell aggregates from horseradish hairy roots encapsulated in alginate gel with paraffin coat

Cell aggregates (CA) derived from horseradish hairy roots were used as inclusion materials for artificial seeds by entrapping them in alginate gel capsules. Regeneration of adventitious roots from the encapsulated CA was suppressed by covering the capsules with thin paraffin coats throughout storage of the capsules. The CA in coated capsules stored at 25°C up to 60 d retained root regeneration potential comparable to that of CA which were not subjected to storage. Plantlets were formed from the roots emerging from the CA in the capsules cultured under light condition.     

Thermotropic behavior of sphingophospholipids of marine invertebrates

Thermotropic behavior of total fraction of sphingomyelin (SM) and its forms, sphingomyelin that contains acyl residues of normal fatty acids (SMN) and sphingomyelin that is Nacylated predominantly with hydroxy acids (SMH) as well as of ceramideaminoethylphosphonate (CAEP) has been studied by the method of differential scanning microcalorimetry. It was shown that chromatographically pure anhydrous sphingophospholipids isolated from different species of marine invertebrates have no phasic transitions in the entire temperature interval of scanning, from-100 to 100°C, whereas partially hydrated samples or mixtures of sphingophospholipids with glycerophospholipids (phosphatidylcholine or phosphatidylethanolamine isolated from corresponding marine invertebrates had phasic transitions in a large temperature range with thermoabsorption maxima in the areas of -40–20°C and 20–80°C. It is suggested that sphingophospholipids, as compared to marine invertebrate glycerophospholipids, have a much lower capability for self-organization, and to form regular supramolecular sphingophospholipid structures both in artificial systems and in biomembranes, such orientants as glycerophospholipids and water are necessary. Possible causes of an unusual behavior of sphingophospholipids of marine invertebrates as compared to glycerophospholipids are discussed.